Igniter assembly for stoker-fired heaters and furnaces



March 1967 J. L. MARGETTS 3,311,075

IGNITER ASSEMBLY FOR STOKER-FIRED HEATERS AND FURNACES Filed Oct. 13.,1965 I NVEN TOR. JOHN L. MARGETTS ATTORNEYS United States Patent3,311,075 IGNITER ASSEMBLY FOR STOKER-FIRED HEATERS AND FURNACES John L.Margetts, 2182 Berkley Ave., Salt Lake City, Utah 84109 Filed Oct. 11,1965, Ser. No. 494,841 8 Claims. (Cl. 110-45) This invention relates toStoker-fired, coal burning heaters and furnaces, and is particularlyconcerned with igniter means for them.

There has long been a need for a satisfactory igniter means that will,on demand, initiate combustion of coal and/or other solid fuels fed intothe retort of a heater or furnace. As a result, there have been a numberof systems developed to ignite solid fuels. Some of these, such as thatshown in US. Patent No. 2,237,237, granted April 1, 1941, require asupply of gas for a gas burner that is ignited through a pilot burnerregulated by an electrical control system. The torch thus formed is usedto ignite the solid fuel. Others, such as that shown in US. Patent No.2,738,742, granted March 20, 1956, simply use an electric heatingelement, having a control circuit to regulate its operation, placed indirect contact with the solid fuel.

However, a gas supply is not always available, nor-de sired, for usewith an igniter means, and heating elements placed in direct contactwith solid fuel frequently become overheated, and burn out, because theheat they generate is not dissipated quickly enough and/or because ofthe intense heat created as the fuel around them burns.

It is an object of the present invention to provide a long-lastingigniter means that will, upon demand, automatically initiate combustionof the solid fuel used in a stoker-fired heater or furnace.

The principal feature of the invention is a special insulated tuyereincorporating an electric heating element and forming a portion of thetuyere ring of the heater or furnace retort. Combustion air moving pastthe special tuyere transfers heat to fuel in the retort and prevents anyheat accumulation sufficient to burn-out the heating element. Theinsulation on the special tuyere prevents heat dissipation throughadjacent tuyeres and localizes heat at its source so that it can beefficiently transferred, through conduction to pieces of coal contactingthe special tuyere, and, by convection with the entering combustion air.

There is shown in the accompanying drawings specific embodiments of theinvention representing what are presently regarded as the best modes ofcarrying out the generic concepts in actual practice. From the detaileddescription of these presently preferred forms of the invention, othermore specific objects and features will become apparent.

In the drawings:

FIG. 1 is a side elevation view, partially broken away to show theretort and stack of a Stoker-fed heater embodying the invention;

FIG. 2, an enlarged, fragmentary, perspective view of the portion of thetuyere ring including the special tuyere of the invention;

FIG. 3, a top plan view of the special tuyere;

FIG. 4, an end elevation view of the special tuyere;

FIG. 5, a vertical section taken on the line 5-5 of FIG. 3;

FIG. 6, a schematic wiring diagram;

FIG. 7, a side elevation view of another embodiment of special tuyerewith the retort bowl of a heater shown fragmentarily in verticalsection; and

FIG. 8, a view in vertical section taken on the line 8-8 of FIG. 7.

3,311,075 Patented Mar. 28, 1967 Referring now to the drawings:

In the embodiment of the invention illustrated in FIGS. l-5, a specialtuyere 10 forms a portion of a tuyere ring of a retort 11 in a heatershown generally at 12.

Coal is fed in customary manner upwardly through the retort from a tube13 having the usual feedscrew or other conveyor means therein.

Air is supplied to the retort, also in customary manner, from a plenumchamber 14. The air is forced through an opening 15 between the standardtuyeres forming the upper edge of retort 11 and an outwardly flared,upwardly extending end of tube 13, that forms a retort bowl 16. Spacers16a, FIG. 1, located at intervals around the retort bowl hold the bowland tuyere ring separated.

Insulation 17, shown best in FIGS. 4 and 5, holds special tuyere 10 inplace while insulating it from the tuyere ring.

The special tuyere 10 is constructed to replace a conventional tuyereand to interlock with conventional tuyeres 18 and 19 adjacent thereto inthe same manner as the usual tuyere it replaces. Thus, the specialtuyere 10 shown in FIGS. l-4 includes an outer shell 20 made of castiron containing at least one percent chromium, or of other good heatconducting but long wearing materials. A central bore 21 is providedwithin the shell, and a cartridge-type heater element 22 is positionedtightly within bore 21. The lead wires from element 22 trail out thebottom of the bore for connection in a temperature responsive controlcircuit. In practice, a cartridgetype heating element such as thatdisclosed in U.S. Patent No. 2,831,951, issued April 22, 1958, to GeorgeB. Dislodge has been found quite satisfactory for the purpose.

A lug 23 that protrudes from one side of shell 20 is adapted to slideinto a groove provided therefor in tuyere 19. Similarly, groove 24formed on the other side of shell 20 is adapted to receive a lugprotruding outwardly from tuyere 18. Thus interlocked, the tuyeres 18and 19, together with the remainder of the standard tuyeres and thespecial tuyere 10, form the ring that serves as the upper peripheraledge of the retort.

Layers 'of insulating material 25 and 26 at opposite sides of shell 20prevent undesired dissipation of heat from shell 20 to the adjacentstandard tuyeres 18 and 19.

In operation, a conventional thermostat 27, FIG. 5, acting in responseto a drop in atmospheric or room temperature closes the control circuitto initiate operation of a motor 28 that powers the conveyor meansWithin tube 13 to supply coal to the firebowl. A separate motor and fanunit can be employed, or if desired, the same motor may supply the powerto drive a fan providing pressurized combustion air to the firebowl, inthe manner fully disclosed in my copending application Ser. No. 469,813,filed July 6, 1965.

If the temperature within the exhaust stack opening 29 of the furnace,FIG. 1, is below a predetermined minimum, for example F., the movablecontact of a temperature responsive element 30, FIGS. 1 and 5,positioned to have a temperature responsive member within the stack,will close and complete the circuit to the cartridge-type heater element22. This energizes the heating element and heats up the surroundingshell 20. Insulation layers 25 and 26 prevent any significant heattransfer from special tuyere 10 to adjacent tuyeres 18 and 19, and theheat is localized in the vicinity of the special tuyere.

The air from plenum chamber 14 that passes through the opening 15between the standard tuyeres and the retort "bowl carries heat away fromthe special tuyere and '3 Q intoth-e coal. As the coal is fed upwardlythrough the firebowl, pieces thereof are constantly moved intoengagementwith the special tuyere, and the entering combustion airalso:directs heat created by the burning of that coal ignited by directcontact with the special tuyere toward the center; of the: retort.

This prevents a heat build-up in the vicinity of the special tuyere thatwill cause the heater element 22 to burn out. If the temperature in thestack isiat or above the predetermined minimum, the contact:oiztemperature responsive element 30 will remain open and the heatingelement 22 will not be energized. Of course, if thestack temperature isat the predetermined minimum there .will already be a fire in the retortand it will not be necessary for the heating element to operate.

In'FIGS.:6 and 7, I show another form of igniter unit ofthe invention.This embodiment also includes a shell 31 of heat conductive, strongmaterial such as cast iron having at least one percent chromium, with agroove 32 in one side and a lug 33 on the other to facilitateinterlocking "with conventional tuyeres. However, in this instance, theshell includes an upper head portion 31a, a depending lip 31b, andalower body portion 310. The lip 31b is adapted to rest on the edge oftuyere bowl 34, shown fragmentarily in section, with only a layer ofinsulating material .35 separating them. As in the previously disclosedembodiment, insulating layers 36 and 37 at the sides of the specialtuyere limit heat transfer from thespecial tuyere to the adjacentstandard tuyeres. Also,

as in the previously disclosed embodiment a cartridge type .heatingelement 3S.is used, but, instead of extending portion 31a :'Of shell 31and from the burning coal in I contactwith the shell toward the centerof the firebowl,

thus preventing a destructive heat accumulation at the heating element.The cooling effect of the air can be regulated merely by changing thesize of bore hole 40.

Whereas there .is here illustrated and specifically described certainpreferred constructions of apparatus which are presently regarded as thebest modes of carrying out the invention, it should be understood thatvarious changes may be made and other constructions adopted withoutdeparting from the inventive subject matter particularly pointed out andclaimed herebelow.

Iclaim:

1. An igniter assembly for Stoker-fired heaters and the like comprisinga shell of heat conducting, long wearing and fire resistant material,said shell having means thereon adapted to interlock it between tuyeresof a heater; a layer of insulating material on each side of the shellthat is adapted to be in engagement with an adjacent tuyere; and anelectrically energized heating element extending into said shell. 1

2.The igniter assembly of claim 1, wherein the shell is of cast-iron.-

3. The igniter assembly of claim 1, wherein the shell is shaped as atuyere and is adapted to form a portion of a retort of a heater.

4. The igniter assembly of claim 1, wherein the heating element is anelongate cartridge-type heater.

5. The igniter of claim 4, wherein the cartridge-type heater extendsupwardly into the shell through a bottom portion thereof.

6. The igniter of claim 4, wherein the cartridge type heater extendsupwardly past a bottom portion of the shell and into a top portion.

7. In combination, a Stoker-fired heater having a retort including anouter ring of tuyeres; a coal-feed tube through which coal is fedupwardly to the retort; an electric cartridge-type heater element in oneof said tuyeres; means insulating said one tuyere from the tuyeresadjacent thereto; means for supplying air to said furnace interior ofsaid ring of tuyeres; and circuit means for energizing said heaterelement on demand.

8. The combination of claim 7, wherein the circuit 7 means includes athermostat responsive to room temperature, and a temperature responsiveelement responsive to the temperature in an exhaust stack of thefurnace.

References Cited by the Examiner UNITED STATES PATENTS 2,210,720 8/1940Johnson et al. ll01 2,540,278 2/1951 Molotzah 1l01 2,851,972 9/ 1958Campbell 1lO-1 KENNETH W. SPRAGUE, Primary Examiner.

1. AN IGNITER ASSEMBLY FOR STOKER-FIRED HEATERS AND THE LIKE COMPRISINGA SHELL OF HEAT CONDUCTING, LONG WEARING AND FIRE RESISTANT MATERIAL,SAID SHELL HAVING MEANS THEREON ADAPTED TO INTERLOCK IT BETWEEN TUYERESOF A HEATER; A LAYER OF INSULATING MATERIAL ON EACH SIDE OF THE SHELLTHAT IS ADAPTED TO BE IN ENGAGEMENT WITH AN ADJACENT TUYERE; AND ANELECTRICALLY ENERGIZED HEATING ELEMENT EXTENDING INTO SAID SHELL.